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Chairs Arms
Why do you speed up while spinning when you bring your arms in?
Say you’re spinning around in an office chair with your arms and legs outstretched. When you pull your arms and legs in so that you’re a tight little ball, you begin to spin faster. The effect seems to become more pronounced if you hold something heavy in your hands. If anybody could help me understand this that would be great. Thanks.
I figured it was probably a matter of conservation of momentum, but what makes the momentum the same for something bigger that spinning slower and something smaller that’s spinning faster if they have the same mass?
The reason is conservation of angular momentum which
means the angular momentum of a system remains constant if the net external torque acting on the system is zero.
So no matter you are outstretched or not your angular momentum is constant because there is no net external torque exerted on you.
angular momentum (P) = (angular velocity) x (moment of inertia about the rotational axis)
moment of inertia of a particle = m.r²
m is the mass of the object
r is the radius of the object
as you see moment of inertia is depended on the distance from particles of the object from the rotational axis.
when you are outstretched particles of your body is spread more away from the rotational axis than when you are not.
so your moment of inertia is larger when you are outstretched
than when you have pulled your arms towards your self.
but according to the principle of conservation of angular momentum, the angular momentum is constant.
angular momentum = I *ω
so when moment of inertia(I) goes down the angular velocity(ω) increases. because angular momentum doesn’t change.
if the object’s mass is relatively larger the change in the moment of inertia is more. which causes the increase in angular velocity to be relatively larger when your reduce the distance to the particles.
————————————————————————
the rotational motion version of F= ma is Τ = I.α
T is net torque, I is moment of Inertia, α is rotational acceleration.
ω’ = ω + α.t
ω’ is the final angular velocity
ω is the initial angular velocity
t is the time difference
α = (ω’ – ω) / t
T = I.(ω’ – ω) / t
if moment of Inertia changes,
when multiplying the inside of the bracket we should consider it.
I is initial moment of inertia
I’ is final moment of inertia
T * t = I’.ω’ – I.ω
The Principle of conservation of angular momentum is only applicable if the net torque on the system is zero.
so T is 0 in this instance.
0 * t =I’.ω’ – I.ω
0 = I’.ω’ – I.ω
I.ω = I’.ω’
that means
initial angular momentum = final angular momentum
OK we’ve proved the principle.
now don’t ask how comes F = ma
it’s basics which’s proven practically it’s the foundation of the theories. of course isn’t 100% correct according to Einstein’s Relativity but almost completely correct when dealing with relatively small velocities.
——–narendrafd@gmail.com
Chairs Arms
How To Find The Right Conference Room Chair
It can be quite challenging indeed when you select the right Conference Room chairs. You may want to consider several things, such as the comfort of your clients and guests, along with staying on a budget – all without compromising your professional appearance.
Seeing as how your guests and clients may be sitting for extended periods of time, the chairs you choose should be ergonomic for all body types. The more comfortable the chairs in your conference room are, the less likely your guests will have to take breaks or get up during meetings.
Several conference room chairs will offer a contoured seat and back that will allow you to adjust the height and also the angle of the chair for better lumbar support. Most offer a swivel mechanism that will allow you to move from side to side with little to no effort. You can also get sturdy wheels as well, which is ideal for sliding across the floor even carpet.
If you don’t want to scratch the floor, you can get rubber tipped casters on the rollers. Conference room chairs also feature tilt tension to keep muscles flexible during meetings. You can also add chair arms as well, which will help to provide extra support and also help guests and clients maintain good posture.
You should also consider the look as well as the feel of your conference room chairs. If at all possible, you should try to select designs and colors that match the current look of your office or conference room. You’ll want all the chairs for the room to be consistent with both style and color.
A majority of chair manufacturers will allow you to customize the upholstery of the back and the seat with leather, synthetic blends, padded foam, or even stitched fabrics. To make the chair look a bit more professional, you can also have the arms of the chair upholstered.
When you spend the money on a Conference Chair, you can’t go wrong simply because of the durability these chairs have to offer. They offer strong frames and quality mechanics, making them last anywhere from 10 – 15 years. In addition to this, most manufacturers will offer limited lifetime warranties as well on these chairs to protect your investment in the long run. These types of warranties will cover the frame, mechanisms, and even severe rips in the upholstery.
A conference room chair is a great investment for any office, as it will keep your guests and clients very comfortable during those important meetings. A conference room without a conference chair just doesn’t make any sense at all.
Why do you speed up while spinning when you bring your arms in?
Say you’re spinning around in an office chair with your arms and legs outstretched. When you pull your arms and legs in so that you’re a tight little ball, you begin to spin faster. The effect seems to become more pronounced if you hold something heavy in your hands. If anybody could help me understand this that would be great. Thanks.
I figured it was probably a matter of conservation of momentum, but what makes the momentum the same for something bigger that spinning slower and something smaller that’s spinning faster if they have the same mass?
The reason is conservation of angular momentum which
means the angular momentum of a system remains constant if the net external torque acting on the system is zero.
So no matter you are outstretched or not your angular momentum is constant because there is no net external torque exerted on you.
angular momentum (P) = (angular velocity) x (moment of inertia about the rotational axis)
moment of inertia of a particle = m.r²
m is the mass of the object
r is the radius of the object
as you see moment of inertia is depended on the distance from particles of the object from the rotational axis.
when you are outstretched particles of your body is spread more away from the rotational axis than when you are not.
so your moment of inertia is larger when you are outstretched
than when you have pulled your arms towards your self.
but according to the principle of conservation of angular momentum, the angular momentum is constant.
angular momentum = I *ω
so when moment of inertia(I) goes down the angular velocity(ω) increases. because angular momentum doesn’t change.
if the object’s mass is relatively larger the change in the moment of inertia is more. which causes the increase in angular velocity to be relatively larger when your reduce the distance to the particles.
————————————————————————
the rotational motion version of F= ma is Τ = I.α
T is net torque, I is moment of Inertia, α is rotational acceleration.
ω’ = ω + α.t
ω’ is the final angular velocity
ω is the initial angular velocity
t is the time difference
α = (ω’ – ω) / t
T = I.(ω’ – ω) / t
if moment of Inertia changes,
when multiplying the inside of the bracket we should consider it.
I is initial moment of inertia
I’ is final moment of inertia
T * t = I’.ω’ – I.ω
The Principle of conservation of angular momentum is only applicable if the net torque on the system is zero.
so T is 0 in this instance.
0 * t =I’.ω’ – I.ω
0 = I’.ω’ – I.ω
I.ω = I’.ω’
that means
initial angular momentum = final angular momentum
OK we’ve proved the principle.
now don’t ask how comes F = ma
it’s basics which’s proven practically it’s the foundation of the theories. of course isn’t 100% correct according to Einstein’s Relativity but almost completely correct when dealing with relatively small velocities.
——–narendrafd@gmail.com
office guest chairs with arms
